Oilpan: Remove support for tracing of off-heap ListHashSets.

Source/core/html/forms/FormController.cpp

 /*
  * Copyright (C) 2006, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010, 2011, 2012 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 368 matching lines @@
 
 PassRefPtrWillBeRawPtr<DocumentState> DocumentState::create()
 {
     return adoptRefWillBeNoop(new DocumentState);
 }
 
 DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(DocumentState)
 
 void DocumentState::trace(Visitor* visitor)
 {
+#if ENABLE(OILPAN)
     visitor->trace(m_formControls);
+#endif
 }
 
 void DocumentState::addControl(HTMLFormControlElementWithState* control)
 {
     ASSERT(!m_formControls.contains(control));
     m_formControls.add(control);
 }
 
 void DocumentState::removeControl(HTMLFormControlElementWithState* control)
 {
@@ skipping 153 matching lines @@
 {
     m_documentState->addControl(&control);
 }
 
 void FormController::unregisterStatefulFormControl(HTMLFormControlElementWithState& control)
 {
     m_documentState->removeControl(&control);
 }
 
 } // namespace WebCore